This proposal reflects a history of 25 years of interest in biological energy-coupling, studied in mammalian mitochondria and microorganisms. More exactly, it is based on the view that every biochemical system retains evidence of its own evolutionary history. The situation is symmetrical: one can examine the course of evolution by studying its product but one can, just as well, learn about existing mechanisms by seeing how they arose. We hope to apply this principle by studying energy conserving events in the, extremely-primitive, thermoacidophilic archaebacteria (eocytes). These organisms appear to have arisen at a very early stage in evolution, in thermal upwellings that are extremely rich in phosphate. We hypothesize that such organisms originally obtained energy in the form of translocated pyrophosphate and, later, came to synthesize pyrophosphate, using a chemiosmotic phosphate circuit. Proton chemiosmosis arose still later by cotransport of phosphate and hydrogen ion, so that proton and phosphate gradients (and fluxes) became inextricably linked. This project will be an investigation of bioenergetics in the eocyte, Sulfolobus acidocaldarius with emphasis on phosphate transport and the ability of pyrophosphate to serve as energy carrier. Energy requirements for phosphate transport will be investigated in the form of possible coupling to cation gradients. Finally, possible phosphate requirements for energy- linked events, such as the energy-requiring reversal of the respiratory chain, will be sought. It could be argued that direct medical consequences of this study are assured (eocytes with optimum growth at from 70 degrees - 90 degrees do not make convincing pathogens). It should be said, however, that our interest in fundamental aspects of membrane bioenergetics earlier led to a 10-year foray (with a number of publications) into the membrane biochemistry of Duchenne and myotonic muscular dystrophy.